In hydropower plants it is often necessary to provide a grating upstream of is the water turbine in order to prevent objects, such as dead animals, plants, wastes etc., flowing in the water to reach the turbine. These could otherwise disturb the operation or even damage the turbine.
For a water turbine operating in running water, the power that can be generated from the water depends on many factors. An important factor is the mass flow rate to which the turbine is exposed, i.e. the product of the mass and the velocity of the water. Further the turbine facing the water flow will be unevenly affected in different parts of its face against the water. In some parts the contribution to the power generation is high, in other parts smaller and in some parts even negative for certain kinds of turbines. An uneven distribution of the contribution to the power generation is in principle present for most types of water turbines. However this is particularly the case for turbines having a shaft perpendicular to the main direction of the water flow, such that the water passes the turbine in the radial direction. For such turbines half of the turbine rotates against the direction of the water flow and on this side the contribution to the power generation is negative.
Most hydropower plants are operated in rapid running water where the high velocity is obtained by a substantial vertical fall of the water. The energy density in the water is high, and the water flow is optimally directed to the turbine. The high power output thus received is based on making use of the potential energy of a higher level when it is transferred to kinetic energy in the rapid flow through the turbine.
A large, not yet much exploited energy source, however can also be found in slowly running water, such as calm rivers, sea currents and tide currents. Although the velocity here is much lower than in conventional hydropower plants the water volume is very high. In the product mass×velocity representing the kinetic energy in the water, the factor mass in such a hydropower plant is much more dominating then in a conventional plant. Since the velocity is small, changes in the velocity can affect the kinetic energy of the water considerably.
Therefore the result of an uneven distribution of the contribution to the generated power discussed above is more important to pay attention to in these types of plants.
The object of the present invention is to optimize the output of a water turbine in a hydropower plant in consideration of the uneven distribution in the turbine of the contribution to the power generation.